The production of paper rolls is known to involve cutting transversally the logs, produced by a rewinding machine, by using one or more cutting-off machines.
A cutting-off machine for logs is described in details in the patent IT 1247330.
Essentially, a cutting-off machine of this type comprises:
a plurality of channels or guides into which the logs are discharged and in correspondence of which movable devices, so-called “porters” in jargon, are mounted to drive the logs into longitudinal motion by pushing them from behind;
a cutting station, comprising one or more circular blades, rotating about axes parallel to those of the logs and fixed on a corresponding movable support.
During the normal operation, a log to be cut is disposed, by a relevant porter, in a preset position on the respective guide and blocked in such position; then, one of the blades is actuated, that is, it is driven into a plane orthogonal to the axis of the log, so as to form a shorter roll of preset size therefrom. The length of the roll depends, actually, on the advancement of the porter during the time elapsing between two consecutive cuts operated by the blades.
In particular, the feeding of the logs to the cutting means is of discontinuous nature, as an empty space results all the time between one log and the next, and because it is in fact impossible to use the system with porters of known type to feed the logs continually.
Such discontinuity in the supply brings about a decreased production, in terms of number of rolls per hour being produced, with respect to the actual capacity of the system. A further drawback is that the components of the system are likely to collide with each other in case of failures in the system predisposed for moving the porters and the cutting means in synchronism, which affects negatively the economy of the manufacturing process.